A knee MRI is a painless, noninvasive test that produces clear pictures of your muscles, tissues and knee joint. This allows your doctor to see your injuries or conditions that may be causing knee pain and discomfort, and then administer the appropriate treatment to relieve those symptoms and improve your life.
A magnetic resonance imaging (MRI) machine uses a large magnet and radio wave pulses to create detailed pictures of your knee. The images show structures of the knee that cannot be seen as well with other types of tests, such as an X-ray or ultrasound. The radiologist will evaluate your MRI results and report them to you and your provider.
MRI is most often used to diagnose knee ligament, cartilage and meniscus tears, as well as other problems that affect the joint and surrounding tissues. The radiologist can also use the images to monitor changes in your knee over time and help guide your treatment plan.
An MRI is the best way to evaluate a partial or complete tear of the anterior cruciate ligament (ACL). This ligament is important in stabilizing your knee joint and keeping it aligned when you walk, run, jump or twist at the knee. An MRI can detect ACL tears and other types of ligament damage, as well as other knee problems that can be caused by overuse, such as tendonitis or osteoarthritis.
When a person has a displaced or swollen meniscus, the MRI shows that part of the cartilage has shifted away from its normal triangular shape. This is referred to as a cleft or “ghost” meniscus, and it can lead to pain and accelerated knee degeneration. An MRI can also identify other types of knee meniscal tears, such as radial or posterior horn tears.
A radiologist can also use an MRI to diagnose knee osteoarthritis, which is a wearing of the cartilage within your knee joints. It can cause stiffness, pain and swelling in the knees. An MRI can also determine the extent of the knee osteoarthritis, whether it is mild to moderate or severe.
During an MRI, you will lie on a table that moves into the magnet of the MRI machine. The radiologist will be outside of the room, but can speak to you through a two-way intercom. You will hear humming, clicking and knocking noises from the MRI machine, which can be distracting and noisy. You may be given earplugs or headphones to help mask the noise.
Your doctor may also give you an intravenous (IV) line to inject a contrast dye into your vein to help improve the quality of the images. The contrast agent is called gadolinium, and it has been shown to be very safe. However, if you are breastfeeding, you should wait until after the procedure to breastfeed because the contrast dye can pass into your milk. You should also avoid taking certain medications, including aspirin and some antibiotics, for 48 hours before your MRI exam.